The present application is the national stage under 35 U.S.C. 371 of PCT/IT98/00155, filed Jun. 11, 1998.
The present invention relates to a dynamo-electric machine rotating by electromagnetic induction such as it acts in linear electric motors.
As is well known, the linear electric motor can be thought of as being derived from a normal asynchronous motor by longitudinally sectioning and rectifying both the stator and the rotor.
The operating principle is based on the generation of a magnetic field which varies spatially with uniform rectilinear motion instead of with rotatory motion as occurs in the normal asynchronous motor.
In the asynchronous linear motor, the inductor generates currents on the armature and the interaction between such currents and the inducting field gives rise to an inducting force directed longitudinally.
It is already known that in linear motors there is no dimensional constraint between inductor and armature.
The present invention aims to overcome also the constraint of the extended shape which is the basis for the linear motor.
An example of a linear motor is disclosed in the patent DE 2217466A. The patent discloses an induction motor comprising a disc of electrical conductor and a 3-element stator, each element comprising a core and windings. Another example of a linear motor can be found in GB1282485 A that discloses a ring-shaped rotor carried by fan blades, which extend radially outward from a hub mounted on a central shaft. In any of these documents , the rotor is mounted on a central shaft. An example of a motor having a rotor in the form of a hoop can be found in the document GB2103768A. In this document the stator and the hoop are of semi-cylindrical section and are thus semi-tiroidal in shape.
The main object of the present invention is to realise a dynamo-electric machine, i.e. one operating both as a motor and as a generator, which employs the technology of the linear electric motor to allow realisations not effected so far on a rotating machine.
The invention, as it is characterised by the claims that follow, solves the problem of providing a dynamo-electric machine rotating by electromagnetic induction such as it acts in linear electric motors, which from a general standpoint is characterized in that it possesses a ring-shaped rotor in the form of a flattened annulus, being fitted with at least one circumferential rail engaged with sliding guides, and an inductance coil stator interacting at least with one part of said rotor.
In other words, the present invention allows to realise a linear electric machine which, functioning for instance as a motor, has a linear armature closed in a loop at its ends to serve as a rotor, and a related stator, at least one fixed inductor, interacting with said armature at least on a part of its said loop.
One of the advantages obtained through the present invention essentially consists of the fact that, when said rotor is mounted for rotation on sliding guides, the structure of the machine is essentially hollow, and inside it may be housed various contrivances for the direct integration of the machine itself with systems for the utilisation of mechanical or electrical energy, or both, depending on whether the dynamo-electric machine functions as a motor or as a generator, or as both at subsequent times.
Another advantage is represented by the fact that the rotor of this machine can have a moment of inertia which can be easily modified by varying its radius. Hence it is possible to modify the torque produced for equal amounts of power supplied to the induction coil, in case of operation as a motor, with the consequent optimisation in the various applications. In addition, the need for gears or other reduction and indirect transmission means normally required to adapt the torque produced by the motors to the user is eliminated. In the absence of such reduction and transmission organs, the cost normally required for the utilisation of the mechanical energy is reduced, thanks to a lower number of necessary components, and the final mechanical efficiency is also increased.
With the use of a variable number of modular inductors, the power of the machine can be modified consequently. The invention can have various types of power supply and efficiency, depending on whether it functions as a motor or as a generator.
Yet another advantage of the invention is to allow large efficiencies simply by increasing the scale factor of the embodiments.
Thanks to the simplicity of construction, provided by the modular structure of the machine, its reliability is high, and its maintenance is made easier and does not require the intervention of particularly specialised personnel.
Given its flat and essentially compact structure, the machine according to the invention is easily and conveniently integrated in all its applications, in particular in those having internal spaces with particular volumes and shapes.
Overall, with respect to prior art electric machines, improvements are obtained in all mechanical characteristics, in adaptability, in dimensional and mechanical terms for the applications, in reliability and in servicing.